feat: add cosine similarity algorithm

__tests__/unit/cosine-similarity.spec.ts

@@ -0,0 +1,41 @@
+import cosineSimilarity from "../../packages/graph/src/cosine-similarity";
+
+describe('cosineSimilarity abnormal demo: ', () => {
+    it('item contains only zeros: ', () => {
+        const item = [0, 0, 0];
+        const targetTtem = [3, 1, 1];
+        const cosineSimilarityValue = cosineSimilarity(item, targetTtem);
+        expect(cosineSimilarityValue).toBe(0);
+    });
+    it('targetTtem contains only zeros: ', () => {
+        const item = [3, 5, 2];
+        const targetTtem = [0, 0, 0];
+        const cosineSimilarityValue = cosineSimilarity(item, targetTtem);
+        expect(cosineSimilarityValue).toBe(0);
+    });
+    it('item and targetTtem both contains only zeros: ', () => {
+        const item = [0, 0, 0];
+        const targetTtem = [0, 0, 0];
+        const cosineSimilarityValue = cosineSimilarity(item, targetTtem);
+        expect(cosineSimilarityValue).toBe(0);
+    });
+});
+
+describe('cosineSimilarity normal demo: ', () => {
+    it('demo similar: ', () => {
+        const item = [30, 0, 100];
+        const targetTtem = [32, 1, 120];
+        const cosineSimilarityValue = cosineSimilarity(item, targetTtem);
+        expect(cosineSimilarityValue).toBeGreaterThanOrEqual(0);
+        expect(cosineSimilarityValue).toBeLessThan(1);
+        expect(Number(cosineSimilarityValue.toFixed(3))).toBe(0.999);
+    });
+    it('demo dissimilar: ', () => {
+        const item = [10, 300, 2];
+        const targetTtem = [1, 2, 30];
+        const cosineSimilarityValue = cosineSimilarity(item, targetTtem);
+        expect(cosineSimilarityValue).toBeGreaterThanOrEqual(0);
+        expect(cosineSimilarityValue).toBeLessThan(1);
+        expect(Number(cosineSimilarityValue.toFixed(3))).toBe(0.074);
+    });
+});

package.json

@@ -21,7 +21,7 @@
     "build:ci": "pnpm -r run build:ci",
     "prepare": "husky install",
     "test": "jest",
-    "test_one": "jest ./__tests__/unit/kCore.spec.ts",
+    "test_one": "jest ./__tests__/unit/cosine-similarity.spec.ts",
     "coverage": "jest --coverage",
     "build:site": "vite build",
     "deploy": "gh-pages -d site/dist",

packages/graph/src/cosine-similarity.ts

@@ -0,0 +1,29 @@
+import { Vector } from "./vector";
+
+/**
+Calculates the cosine similarity
+@param item - The element.
+@param targetItem - The target element.
+@returns The cosine similarity between the item and the targetItem.
+*/
+const cosineSimilarity = (
+    item: number[],
+    targetItem: number[],
+): number => {
+    // Vector of the target element
+    const targetItemVector = new Vector(targetItem);
+    // Norm of the target element vector
+    const targetNodeNorm2 = targetItemVector.norm2();
+    // Vector of the item
+    const itemVector = new Vector(item);
+    // Norm of the item vector
+    const itemNorm2 = itemVector.norm2();
+    // Calculate the dot product of the item vector and the target element vector
+    const dot = targetItemVector.dot(itemVector);
+    const norm2Product = targetNodeNorm2 * itemNorm2;
+    // Calculate the cosine similarity between the item vector and the target element vector
+    const cosineSimilarity = norm2Product ? dot / norm2Product : 0;
+    return cosineSimilarity;
+}
+
+export default cosineSimilarity;